Biohazardous waste is any by-product of a biological, organic, pathological, or pharmaceutical process or method with the potential to endanger the health of humans and other life forms through infection or other means. Thus, "biohazardous" is broader in meaning than "infectious" or "infectious medical". For example, biohazardous waste encompasses organic wastes such as pharmaceutical waste, veterinary waste, food waste, and medical wastes.
Medical infectious waste is a serious concern because it can infect humans with deadly organisms such as the AIDS and hepatitis viruses. Such infectious waste is generated by hospitals and medical and veterinary care facilities as a by-product of their health and laboratory services. Due to the public awareness raised by AIDS, many have expressed concerns about unregulated and unauthorized disposal of medical waste.
The prior art has attempted to address the problem of disposing of medical waste by methods such as specialized land filling, incineration, steam autoclaving, ETO gas exposure, chemical treatment, radiation exposure (Gamma), microwave heating, and radio-frequency (RF) or dielectric heating. Incineration currently is the most popular method employed to dispose of medical and veterinary waste. However, incineration may produce gaseous emissions that may contain high levels of toxic heavy metals, e.g. cadmium, chromium, lead, mercury, dioxins and furans generated by the plastics and metallic content derived from syringes, needles, and sharps included in the waste.
Steam autoclaving is another known method for treating medical waste. Steam autoclaving is a thermal process in which the wastes are sterilized by exposure to high-temperature steam. The high temperature and good penetrability of steam effectively destroys the infectious agents. Since the waste is rendered sterile, it can be directly landfilled. However, for steam autoclaving to be an effective treatment method, the steam must fully penetrate the waste to guarantee that all infectious microorganisms are killed. Also, since autoclaved waste is neither mechanically destroyed nor significantly reduced in volume, it is still recognizable as medical waste.
U.K. Pat. No. 2,232,594 to Goldher et. al. and PCT application No. US91/02451 to Mertsch et. al. teach a process and apparatus for disinfecting medical waste using a combination of steam preheating, microwave heating, and conventional methods of conduction heating. The major drawbacks of these methods relate to the complexity and inefficiency of the plants due to the numerous heating methods and microwave energy sources required, as well as lack of control of steam formation during heating. For example, Mertsch et. al. requires pretreating the waste by exposure to steam and that the steam should be used to "build up overpressure" in the microwave chamber containing the waste for faster heating of the waste. Goldner et. al. requires use of a "temperature maintenance chamber" to supplement the heating produced by the microwave sources and to prevent the waste from "cooling". Also, since neither of these approaches control moisture content of the air, excessive steam formation can cause inefficient use of the microwave energy. In addition, microwave heating of medical waste has the disadvantage that the short wavelengths of microwaves limit their penetration. In contrast, the radio-frequency (RF) waves employed in the present invention have longer wavelengths, and penetrate more effectively.
U.S. Pat. No. 5,106,594 discloses disinfecting and processing medical waste by RF radiation and converting the disinfected waste into reclaimed plastic or low-sulfur fuel. The apparatus of U.S. Pat. No. 5,106,594 breaks up the waste into fragments, compresses the waste fragments to achieve volume reduction, disinfects the compressed waste fragments using a dielectric heater, and converts the disinfected waste into useful material by using reclamation equipment. A drawback of this method and apparatus, however, is that the medical waste is only disinfected rather than sterilized. Also, the method is time-consuming because after the waste is heated in the RF chamber, at least one hour of standing time is required outside the RF chamber to achieve a safe level of disinfection- The present invention, however, typically achieves neutralization in about 1/3 the time required by the art.
Although the prior art devices provide for waste disposal, a long-term solution to the medical waste disposal problem must address and satisfy basic requirements. Medical waste disposal must be safe, efficient, and should reduce, if not completely eliminate, the risk of infection to humans. A need therefore exists for a method and apparatus for neutralizing or destroying the infectious potential of biohazardous waste, in particular, medical waste, and to transform it into a material which does not adversely impact the environment.